A test that asserts on peak memory

An N+1 fixed by eager loading can be replaced by a memory problem, and a query-count assertion reports the page as healthy while it hydrates forty thousand objects.

public function testTheExportStreamsRatherThanBuffers(): void
{
    factory(Order::class, 5000)->create();

    $before = memory_get_peak_usage(true);
    $this->artisan('export:monthly')->assertExitCode(0);

    $this->assertLessThan(
        64 * 1048576,
        memory_get_peak_usage(true) - $before,
        'the export is buffering again'
    );
}

Peak rather than current is the measurement, because the whole point is the high-water mark during the run. true as the argument reports memory allocated from the system rather than by PHP, which is the number that matters for a limit. Five thousand rows is what makes the assertion meaningful — with fifty, a buffering implementation passes comfortably.